tools/CrashHandler.cpp

#include "CrashHandler.h"

#include "SkTypes.h"

#include <stdlib.h>

#if defined(SK_BUILD_FOR_MAC)

// We only use local unwinding, so we can define this to select a faster implementation.
#define UNW_LOCAL_ONLY
#include <libunwind.h>
#include <cxxabi.h>

static void handler(int sig) {
    unw_context_t context;
    unw_getcontext(&context);

    unw_cursor_t cursor;
    unw_init_local(&cursor, &context);

    SkDebugf("\nSignal %d:\n", sig);
    while (unw_step(&cursor) > 0) {
        static const size_t kMax = 256;
        char mangled[kMax], demangled[kMax];
        unw_word_t offset;
        unw_get_proc_name(&cursor, mangled, kMax, &offset);

        int ok;
        size_t len = kMax;
        abi::__cxa_demangle(mangled, demangled, &len, &ok);

        SkDebugf("%s (+0x%zx)\n", ok == 0 ? demangled : mangled, (size_t)offset);
    }
    SkDebugf("\n");

    // Exit NOW.  Don't notify other threads, don't call anything registered with atexit().
    _Exit(sig);
}

#elif defined(SK_BUILD_FOR_UNIX) && !defined(SK_BUILD_FOR_NACL)   // NACL doesn't have backtrace().

// We'd use libunwind here too, but it's a pain to get installed for both 32 and 64 bit on bots.
// Doesn't matter much: catchsegv is best anyway.
#include <execinfo.h>

static void handler(int sig) {
    static const int kMax = 64;
    void* stack[kMax];
    const int count = backtrace(stack, kMax);

    SkDebugf("\nSignal %d [%s]:\n", sig, strsignal(sig));
    backtrace_symbols_fd(stack, count, 2/*stderr*/);

    // Exit NOW.  Don't notify other threads, don't call anything registered with atexit().
    _Exit(sig);
}

#endif

#if defined(SK_BUILD_FOR_MAC) || (defined(SK_BUILD_FOR_UNIX) && !defined(SK_BUILD_FOR_NACL))
#include <signal.h>

void SetupCrashHandler() {
    static const int kSignals[] = {
        SIGABRT,
        SIGBUS,
        SIGFPE,
        SIGILL,
        SIGSEGV,
    };

    for (size_t i = 0; i < sizeof(kSignals) / sizeof(kSignals[0]); i++) {
        // Register our signal handler unless something's already done so (e.g. catchsegv).
        void (*prev)(int) = signal(kSignals[i], handler);
        if (prev != SIG_DFL) {
            signal(kSignals[i], prev);
        }
    }
}

#elif defined(SK_BUILD_FOR_WIN)

#include <DbgHelp.h>

static const struct {
    const char* name;
    int code;
} kExceptions[] = {
#define _(E) {#E, E}
    _(EXCEPTION_ACCESS_VIOLATION),
    _(EXCEPTION_BREAKPOINT),
    _(EXCEPTION_INT_DIVIDE_BY_ZERO),
    _(EXCEPTION_STACK_OVERFLOW),
    // TODO: more?
#undef _
};

static LONG WINAPI handler(EXCEPTION_POINTERS* e) {
    const DWORD code = e->ExceptionRecord->ExceptionCode;
    SkDebugf("\nCaught exception %u", code);
    for (size_t i = 0; i < SK_ARRAY_COUNT(kExceptions); i++) {
        if (kExceptions[i].code == code) {
            SkDebugf(" %s", kExceptions[i].name);
        }
    }
    SkDebugf("\n");

    // We need to run SymInitialize before doing any of the stack walking below.
    HANDLE hProcess = GetCurrentProcess();
    SymInitialize(hProcess, 0, true);

    STACKFRAME64 frame;
    sk_bzero(&frame, sizeof(frame));
    // Start frame off from the frame that triggered the exception.
    CONTEXT* c = e->ContextRecord;
    frame.AddrPC.Mode      = AddrModeFlat;
    frame.AddrStack.Mode   = AddrModeFlat;
    frame.AddrFrame.Mode   = AddrModeFlat;
#if defined(_X86_)
    frame.AddrPC.Offset    = c->Eip;
    frame.AddrStack.Offset = c->Esp;
    frame.AddrFrame.Offset = c->Ebp;
    const DWORD machineType = IMAGE_FILE_MACHINE_I386;
#elif defined(_AMD64_)
    frame.AddrPC.Offset    = c->Rip;
    frame.AddrStack.Offset = c->Rsp;
    frame.AddrFrame.Offset = c->Rbp;
    const DWORD machineType = IMAGE_FILE_MACHINE_AMD64;
#endif

    while (StackWalk64(machineType,
                       GetCurrentProcess(),
                       GetCurrentThread(),
                       &frame,
                       c,
                       NULL,
                       SymFunctionTableAccess64,
                       SymGetModuleBase64,
                       NULL)) {
        // Buffer to store symbol name in.
        static const int kMaxNameLength = 1024;
        uint8_t buffer[sizeof(IMAGEHLP_SYMBOL64) + kMaxNameLength];
        sk_bzero(buffer, sizeof(buffer));

        // We have to place IMAGEHLP_SYMBOL64 at the front, and fill in how much space it can use.
        IMAGEHLP_SYMBOL64* symbol = reinterpret_cast<IMAGEHLP_SYMBOL64*>(&buffer);
        symbol->SizeOfStruct = sizeof(IMAGEHLP_SYMBOL64);
        symbol->MaxNameLength = kMaxNameLength - 1;

        // Translate the current PC into a symbol and byte offset from the symbol.
        DWORD64 offset;
        SymGetSymFromAddr64(hProcess, frame.AddrPC.Offset, &offset, symbol);

        SkDebugf("%s +%x\n", symbol->Name, offset);
    }

    // Exit NOW.  Don't notify other threads, don't call anything registered with atexit().
    _exit(1);

    // The compiler wants us to return something.  This is what we'd do if we didn't _exit().
    return EXCEPTION_EXECUTE_HANDLER;
}

void SetupCrashHandler() {
    SetUnhandledExceptionFilter(handler);
}

#else

void SetupCrashHandler() { }

#endif